The Buffalo Bills posted an operating profit of between $30 million and $40 million last season, sources close to bidding for the team told The Post.

New details of the team’s finances came to light Thursday as the auction for the NFL franchise moved into the second round, sources said.

Profits could rise to $60 million — in line with other teams — if the state builds the Bills a new stadium, a source added.

There are four known bidders for the team, which was put on the block after its owner, Ralph Wilson, Jr., died in March.

The known bidders are: Donald Trump; Terrance Pegula, owner of the NHL’s Buffalo Sabres; rocker Jon Bon Jovi, who is fronting a group of Toronto sports team owners; and Tom Golisano, the billionaire former owner of the
Sabres and three-time candidate for governor of New York.

EJ Manuel and Doug Marrone are heading into their second year as the Bills’ leaders.Photo: AP Trump was the first to meet with team officials as part of the second round of bidding, AP reported. Those bids are expected within three weeks.

During the second round, at the meetings with team officials — some of which are held in Detroit, where the Wilson family lives, and some that are slated for New York City — the bidding groups will receive in-depth financial information on the team to better gauge their offers.

The winning bidder is expected to be selected by Sept. 30 — in time to be presented to owners at a league meeting in early October.

All four bidding groups have sent letters to the NFL agreeing to a background check — although the league usually vets just the people involved in the winning bid, sources said.

Bills fan Anthony Lynch proudly hoists an anti-Bon Jovi poster at a Buffalo bar. The New Jersey rocker is among the bidders for the team.Photo: AP It is expected that the principal owner of each bidding group will be asked to pony up a down payment of roughly 30 percent of their second-round bid, sources said.

NFL rules state that a principal owner can borrow no more than $200 million and must hold at least a 30 percent stake in the club, the AP reported.